1. Field of the Invention
This invention relates to mechanical gearing and more particularly to providing a coupling between gears of a mechanical gearing.
2. Description of Related Art
Gear units which act as transmission gear units and reduction gear units are made up of one or more gearing stages. The gear units may be designed as toothed gears in which, in each gearing stage, a first driving gear wheel engages in a second driven gear wheel. However, toothed gears are subject to wear because of the tooth engagement.
If toothed gears are used as reduction gear units, the driven second wheel has a greater diameter (corresponding to the reduction ratio) than the driving first wheel. If a higher reduction ratio is desired, this may appreciably increase the dimensions of the gearing stage.
For example, in absolute rotational-angle-measuring systems, mechanical reduction gear units are used to determine the rotational angle in an absolute manner over a plurality of shaft rotations. The rotational-angle-measuring systems are, as a rule, coupled to electrical drives which rotate relatively rapidly, with rotational speeds of up to 12,000 revolutions/minute being encountered. Since the bearings for such high rotational speeds are expensive, a high reduction ratio is desirable for the first gearing stage so that a less expensive bearing can be used for the driven second wheel. If a hollow-shaft arrangement is used in such rotational angle measuring systems, the first driving wheel will have a relatively high diameter in order to be mounted on the hollow shaft, which results in a relatively high diameter second driven wheel, due to the desired high reduction ratio. This, in turn, results in a relatively large radial space requirement for the first gearing stage. In addition, the dimensioning of the second driven wheel results in a disadvantageous mass inertia of the driven wheel.
Thus, it is desirable to provide a gearing stage which makes possible small dimensions and a small mass moments of inertia as well as being largely wear-free.